Related Stories

Last time, I talked about the world's most popular dinosaur, Tyrannosaurus rex, and how a convenient accident of fate gave it the splendid name that means 'tyrant lizard king'. It is indeed a scary beast in many ways, including its massive head and huge teeth.

The palaeontologist, John R. Horner, and the science writer, Don Lessem, wrote in their book, The Complete T. rex: "We're lucky to have the opportunity to know T. rex, study it, imagine it, and let it scare us. Most of all, we're lucky T. rex is dead."

By the way, before I get to T. rex's head, let's first look at his other end. T. rex is some kind of king, so it's only right that he should have really kingly droppings. 'Coprolite' is the fancy name for fossilised faeces, that is, animal dung, or poo.

In 1997, the Royal Saskatchewan Museum sent Karen Chin of the US Geological Survey a rather unusual specimen that they had unearthed. It was large (44 centimetres by 16 centimetres by 13 centimetres), nicely tapered and quite heavy (7.1 kilograms).

It turned out to be a Tyrannosaurus poo, and twice as big as any other previously discovered carnivore's poo.

Careful analysis showed that it was full of shattered bones from a plant-eating dinosaur.

Now let's stop mucking about at the back end, and get back to the head.

For many years, the palaeontologists thought that T. rex had the biggest head of any dinosaur. One skull measured 1.5 metres long.

But in 1996, Carcharodontosaurus (meaning 'shark-toothed reptile') was discovered in Morocco. Its head was 1.6 metres long.

Now the T. rex teeth were in a huge jaw, and powered by huge jaw muscles, so they could generate a massive bite force of an enormous 3100 kilograms.

Comparing this to today's animals, it outclasses the 1800 kilograms of bite force of a great white shark, the 560 kilograms of a large African lion, and is much greater than our pathetic human bite force of just 80 kilograms.

On the other hand, T. rex had less bite force than the extinct ancestor of the great white shark, the gigantic Carcharodon megalodon.

This shark, 16 metres long and weighing up to 100 tonnes, could generate up to 18,000 kilograms of bite force.

T. rex had lots of teeth. The biggest tooth found so far is about 30 centimetres long. These teeth sat in a huge jaw, which was U-shaped at the front, not V-shaped like many non-tyrannosaur dinosaurs.

The teeth right at the very front of the upper jaw were curved backwards, and had tips like chisels (like our front teeth).

The rest of the teeth were more robust. The palaeontologists often call them 'lethal bananas'. They were also serrated, with the serrations on the front and rear surface.

On a bread knife, the serrations are set up so that the knife will easily cut the bread without tearing or deforming it.

But in a series of experiments, it was found that the serrations on a Tyrannosaurus tooth won't cut smoothly through raw meat. The teeth are more like pegs that grab, rather than knives that cut. So why are they serrated?

We get a clue from the Komodo dragon of Indonesia, the largest lizard in the world. Its teeth have serrations that are very similar to those of Tyrannosaurus, and they are not very good at cutting.

But the little gaps between the serrations are really good at holding little particles of meat and grease. Komodo dragons don't use dental floss or a toothbrush, so the meat and grease remain on the teeth, and this gives bacteria a really good home to live in.

When a Komodo dragon bites another animal, if the animal doesn't die immediately, the wound nearly always gets infected, and the bitten animal very soon dies from the massive infection.

Now for most of the last century-and-a-half, palaeontologists would find the dinosaur fossils, and then clean, prepare and mount them. They could measure them and examine them carefully for similarities and differences.

But a new field of study is arising: palaeobiochemistry. These palaeobiochemists have recovered about half-a-dozen different biochemicals from a 68-million-year-old T. rex femur (the bone joining the hip to the knee).

These chemicals hinted that T. rex was related to chickens, frogs and newts, somewhere between birds and crocodiles.

This field of dinosaur research is going off like crazy. There will be lots of discoveries still left to make about dinosaurs, for centuries to come.